what the hell is the flex plate

i went to a mechanic and he told me my flex plate must be bad- how do u know if your flex plate is bad, and how much should is job like that cost -- some 1 help my 97 maxima -- she's hurting

Flex plate or flex section? If it's the flex section of your downpipe (y-pipe), then you can either replace it altogether for about $200 with an aftermarket piece and gain some power or you can get just the flex repaired at a muffler shop. Personally, I'd get the aftermarket part as it gets rid of the precats and frees up significant power.

~THT